1. Technical Field
The present invention relates in general to data processing systems, and, in particular, to a system, method, and program for establishing communication among data processing systems. Still more particularly, the present invention relates to a system, method, and program for establishing modem communication between a master computer system and a plurality of slave computer systems through a common serial communication channel.
2. Description of the Related Art
A data processing system typically includes a system processor, a memory system, and an input/output (“I/O”) controller. The data processing system may be coupled in communication with another data processing system. Two data processing systems communicate by coupling a communication device, such as a modem, to the I/O controller of each data processing system and linking the communication devices or modems together through a serial communication channel, such as a telephone line or a wireless communication channel. Interconnect among these devices is usually accomplished using a public switch telephone network.
In one application, the two data processing systems are coupled in communication with each other so that one data processing system directs and executes commands to the other data processing system. For example, one data processing system may be a master computer system that includes at least a master system processor, a master memory system, and a master I/O controller. The other data processing system may be a slave computer system which includes at least a slave system processor, a service processor, a slave memory system, and a slave I/O controller. The service processor is a dedicated special-purpose processor that serves as a full time hardware and software system monitor during the operation of the slave computer system. The service processor monitors the environmental status of the slave computer system and executes various operational or maintenance routines, such as re-configuration of the slave system processor or the slave computer system, execution of the slave computer system under a different configuration, or analysis of performance of the slave computer system and components or sub-systems of the slave computer system. The master computer system is coupled in communication with the slave computer system so that the master system processor is able to direct commands from the master computer system to execute various routines by the service processor at the slave computer system.
When the data processing system is coupled in communication with a plurality of other data processing systems, a separate serial communication channel (e.g., phone line or wireless channel) exists between the data processing system and each of the other data processing systems. However, a plurality of serial communication channels for communicating between the data processing system and each of the various other data processing systems means that the use of a larger amount of communication resources is required. The communication resources are expensive and are not generally used on a regular basis.
In order to reduce expenses and a large amount of communication resources, a single communication channel can be used. The single communication channel couples the data processing system to a centralized hardware box, and the various other data processing systems are also able to couple in communication with the centralized hardware box through a communication switch. The centralized hardware box manages the communication between the data processing system and one of the other data processing systems. Normally, this communication management is done manually requiring an operator to be present. If it is done electronically, then the data processing system initiates a session request or call for a particular data processing system to which the data processing system requests to communicate by sending an indication, such as a certain type of telephonic ring or distinguishing signal, to the centralized hardware box through the single communication channel. The centralized hardware box controls the switch to activate the communication between the data processing system and the requested particular data processing system by switching on the communication channel between the centralized hardware box and the particular data processing system. The existence of the centralized hardware box, however, results in the use of additional hardware and adds to the expense for providing communication between the data processing systems. The present invention recognizes the need and desire to eliminate hardware and reduce expenses associated with providing communication and manual intervention between data processing systems.